Depression is a disease that affects a large proportion of the population and is a result of multiple factors. According to the World Health Organization (WHO), depression ranks among the ten leading causes of disability and will become the second-largest cause of the global health burden by 2020. An estimated 121 million people worldwide suffer from a depressive disorder for which they require treatment. It is estimated that 5.8% of all men and 9.5% of all women will suffer from a depressive disorder in any given year and that 17% of all men and women will suffer from a depressive disorder at some point in their lives.
Several types of antidepressant medications are used to treat depressive disorders, such as selective serotonin reuptake inhibitors (SSRIs), tricyclics, and monoamine oxidase inhibitors (MAOIs). The SSRIs generally have fewer side effects than tricyclics. Thus SSRIs are the most widely used antidepressants today.
Although the condition of many patients improves with medication, only a minority experience full remission, and patients whose condition responds to one medication may not have a response to others. Individual variation in antidepressant treatment outcome is, at present, unpredictable, but may have a partial genetic basis.
There exists a desire for a method to predict the outcome of treatment with antidepressant medication in individuals.